1. Field of the Invention
The present invention generally relates to a disc-shaped information carrier medium such as an optical disc or a magneto-optical disc and, more particularly, to the format of an index region of the information carrier medium.
For the purpose of the present invention, the term "optical disc" hereinafter referred to and used in the appended claims is to be understood as including not only a compact optical disc, but also a magneto-optical disc.
2. Description of the Prior Art
Conventional optical disc, typically contain at least one index region having an index such as the track number provided for each track on the optical disc.
According to the prior art, only the index is recorded in the index region. Therefore, the provision of an index region correspondingly reduces the information storage capacity of the optical disc as a whole. In addition, where the disc contains a substantial amount of information such as a long-time music or video recording or playback such use necessitates a memory buffer for the index region. Which buffer is required to have a relatively large storage capacity making it impossible, or impractical to record the information involving a long-time video or music recording or playback.
In particular, the problem associated with the recording large amounts of information such as the long-time recording or playback has obstructed the development of an digital audio disc or video disc having a capacity large enough to accommodate such information.
In order to eliminate the above discussed problems, the information can be recorded on the index region in a multiplex recording fashion.
However, it has been found that multiplex recording of information on a index region of the optical disc often causes a considerable reduction in signal reproduction quality and cannot provide a support for an error correction.